Commercial signs are designed to display advertising and images for products or services. One type of commercial sign is known in the art as an illuminated sign box. An illuminated sign box includes at least one internal light source for illuminating the advertising graphic that forms part of the display.
One type of illuminated sign box is known as an edge lit sign box. In an edge lit sign box, a frame is provided to support the advertising graphic as well as the light source. The light source is secured to the edge of a light panel, typically an acrylic or glass member formed as a square panel with nearly planar front and back surfaces. The light from the lamp is directed into the edge of the light panel (the light receiving edge) and, due to internal reflection, the light propagates throughout and fills the light panel. The light is then emitted from at least one of the nearly planar surfaces of the light panel (the light emitting face).
To emit the light from the face of the light panel, light dispersion mechanisms are incorporated into the light panel. Such light dispersion mechanisms disrupt the internal reflection of the light within the light panel thereby causing the light to pass through the face of the light panel. Examples of light dispersion mechanisms incorporated into light panels include etched convexities and concavities, as well as printed designs such as lines and dots.
A primary goal of light dispersion mechanisms in sign boxes is to provide the brightest and most uniform emission of light from the face of the light panel. This causes the graphic illuminated within the sign box to be attractively displayed with minimum dark spots. Unfortunately, as the distance from the light source increases, the light intensity diminishes so a noticeably darker portion of the display may result.
One way to combat non-uniform light emission from a light panel is to vary the pattern of the light dispersion mechanism. For example, the light dispersion mechanism may be provided with a spacing, size or both which vary relative to the distance from the light source. If designed properly, such variations may provide a uniform display.
While the above technique of providing uniform displays has achieved great commercial success, there is still room for improvement in the art. For example, conventional techniques for forming light dispersion grooves in light panels rely on mechanical formation techniques such as v-cutting, wherein the grooves are scratched into the surface of the light panel, and engraving, wherein the grooves are routed into the surface of the light panel with a rotating bit. Such mechanical techniques have drawbacks such as the inability to adjust the depth of the groove relative to any contours in the surface of the light panel and the inability to form a groove with discontinuous diffusive properties. Such mechanical techniques are also limited as to the degree of control over the width and depth of the grooves.
More particularly, mechanical techniques vary the depth of the grooves relative to a plane defined above the surface of the light panel by the fixture holding the tool (e.g., the cutter or bit). As such, the depth of the groove formed in the light panel may be varied relative to the plane above the surface of the panel, but the groove depth does not vary relative to contours in the surface of the light panel itself which may be present due to tolerance variations in the panel forming process. In addition, mechanical techniques work continuously so that adjacent portions along the length of the groove are rendered the same. In particular, the diffusiveness of the groove is the same throughout the length of the groove. This limits the achievable brightness of the display. Finally, the brightest, most uniform display requires grooves that barely mark the surface of the panel at the edge of the panel adjacent the light source and dramatically increase toward the center of the light panel. This degree of control is extremely difficult if not impossible with mechanical techniques.
In view of the foregoing, it would be desirable to provide a light panel which is brighter than conventional light panels and a technique for producing the same.